Arancher is mixing two types of food, brand x and brand y for his cattle. if each serving is required to have 60 grams of protein and 30 grams of fat, where brand a has 15 grams of protein and 10 grams of fat and costs 80 cents per unit, and brand b contains 20 grams of protein and 5 grams of fat, and cost 50 cents per unit, how much of each type should be used to minimize cost to the rancher? a. formulate a linear programming model for this problem b. solve this method by using solver method